Purpose: The purpose of this study is to characterize the base-width neutral step (BNS) as the first step in a compensatory step response in persons with moderate Parkinson's disease (PD), and its effect on balance recovery.
Materials and methods: Ten PD and 10 healthy controls (HCs) responded to a posterior waist pull. A BNS was defined if the first step was less than 50 mm. The length, height, duration and velocity of the BNS and its effect on balance recovery time and center of mass location at recovery were compared to the first step within other stepping strategies (single step (SS), multiple step (MS)). A linear mixed model was used to compare across strategies.
Results: Six of ten persons with PD compared to zero HC used a BNS. The BNS was shorter in length and duration compared to MS responses in HC, and shorter in duration compared to MS responses in PD. The BNS was slower in velocity compared to every other strategy. BNS use resulted in a longer recovery time compared to all strategies in HC and SS responses in PD, and trended toward a longer recovery time compared to MS responses in PD.
Conclusions: The BNS as the first step in a MS response may be an unreported strategy for compensatory stepping in PD. This study suggests that the cost of utilizing the BNS may be a longer time for recovery, but further work is necessary to understand the progression of the BNS as PD severity increases.
Keywords: Parkinson's disease; balance recovery; compensatory stepping; motor control.